FIG. 1 depicts an example of a communication system, or an aggregate of multiple communication systems, that interconnects both mobile and computer networks. In the scenario of the figure, a mobile terminal 102 is communicating with a second terminal such as another mobile terminal or a desktop computer 112 reachable via radio access network 104, core (mobile) network 106, a public computer network 108 such as the Internet, and a local area network 110. Alternatively, either of the terminals 102, 112 may communicate with one or more network elements residing in one of the intermediate networks 104, 106, 108, and 110, for example. The figure is merely used to highlight the fact how far-situated two or more communicating parties having access to different networks may actually reside and how different information transfer technologies may be cleverly combined to provide nearly transparent communication experience. As transfer resources, being either wireless (frequencies, etc) or wired (time slots over a copper pair, etc), are in many cases designed for a certain average load only and the number of connections is generally increasing, the unnecessary or “idle” connections between two or more entities shall not be kept alive for unlimited period of time.
Terminal devices and various network elements may be required to execute a plurality of cyclic operations that are to be performed at least once per a predetermined time interval (e.g. once every N seconds or minutes). For example, let us refer to a scenario in which NAT (Network Address Translation) and/or firewall bindings refreshment is required. NAT functionality offers address mapping between two different networks (e.g. a private and a public one) whereas the firewalls monitor and limit traffic on the edge of a network. In practice, NAT and firewall functions may be implemented by the same apparatus, e.g. the GGSN (Gateway GPRS Support Node) of FIG. 1. One operation needed in this context utilizes a so-called keep-alive time, which refers to a time period X prior to or upon the expiration of which the terminal should send a keep-alive message to the NAT/firewall entity concerning each UDP (User Datagram Protocol) and TCP (Transmission Control Protocol) connection thereof, then the associated, connection-specific timer is reset and the same cycle repeats until the connection is finally terminated. For UDP this X may be something like 30 seconds, and for TCP somewhere around 1200 seconds, for example.
As the keep-alive operations are sent separately for each connection, there often are several keep-alive sequences simultaneously running. Particularly in the case of mobile apparatuses that most likely rely on somewhat limited power sources such as a rechargeable battery, constant wake up procedures from a sleep (or other power saving) state for executing each keep alive operation consume an unnecessary amount of power. For example, from idle operation mode (e.g. when there is no call or other payload data transfer ongoing) the wake up procedure causes a power consumption peak that may last for a relatively long time. In the worst case the connection-specific keep-alive transmissions may prevent the mobile apparatus from never really entering a true sleep state, and the apparatus constantly stays in some power inefficient mode instead.